Electric control apparatus

ABSTRACT

Electric control apparatus of electromagnetic type in which the magnetic coil is encapsulated within a detachable insulating housing surrounding the magnetic core, the core and the walls of the housing adjacent the core comprising means for limiting swelling of the resinous material forming the housing when heating of the coil occurs due to an overcurrent, thereby facilitating replacement of the housing.

' United States Patent [191 [111 3,821,671

Grunert et al. June 28, 1974 1 ELECTRIC CONTROL APPARATUS 3,643,190 2/1972 Puetz 335/132 [75] Inventors: Kurt A. Grunert, Beaver; Birch L.

a Industry, both of Primary Examiner-Har0ld Broome [73] Assignee: Westinghouse Electric Corporation, Attorney Agent or Johns Pittsburgh, Pa.

221 Filed: Aug. 29, 1973 211 Appl. No.: 392,697

[5 7] ABSTRACT Electric control apparatus of electromagnetic type in which the magnetic coil is encapsulated within a de- [52] US. Cl. 335/132, 335/281 tachable insulating housing Surrounding the magnetic core, the core and the walls of the housing adjacent the core comprising means for limiting swelling of the resinous material forming the housing when heating of the coil occurs due to an overcurrent, thereby facili- [56] References Cited tating replacement of the housing.

UNITED STATES PATENTS 7 3,368,171 2/1968 Conner et al. 335/132 5 Claims, 6 Drawing Figures PATENFEH JUN 2 8 I974 SHEET 2 BF 3 PATEWEUJUNZB am SHEET 0F 3 FiGB.

FIG4.

BACKGROUND OF THE INVENTION 1. Field of the Invention I This invention relates to an electric control device such as a contactor or relay of the electromagnetic type, and more particularly it pertains to a detachable magnetic coil therefor.

2. Description of the Prior Art Industrial equipment that is operated electrically such as by a motor is usually regulated by a control device which may be a contactor or relay having parts movable between two positions for opening and closing a circuit through the motor. Due to voltage drops in a system or in case of a mechanical blockage, wherein the armature of an electromagnet fails to close upon the fixed magnet,the excess current through the coil is sufficient to cause the coil windings to overheat and ultimately burn out. Where the coil windings are encapsulated within a molded housing of resinous material, the windings cause expansion and contraction of the housing causing distortion of the coil to an extent that it is permanently secured to the magnet core and causes both the coil and core to be unusable.

Associated with the foregoing is the necessity of providing a detachable housing portion in which the coil is encapsulated and which upon failure of the coil windings is sufficiently intact to enable its removable and replacement expeditiously.

SUMMARY OF THE INVENTION It has been found in accordance with this invention that the foregoing problems may be overcome by providing an electric control device of the electromagnetic type comprising an insulating housing having a detachable coil portion, pairs of separable contacts within the housing, means within the housing for moving the contacts between open and closed positions and comprising an electromagnetic control mechanism including a magnetic armature, a magnetic core, and a coil, the detachable housing portion being composed of a resinous material, the detachable housing portion having walls forming opening means for receiving the core, the core comprising a plurality of laminations and a rivet securing the laminations together, the rivet comprising opposite end portions extending into clearance space between the core and the walls forming the opening means, each lamination on the opposite sides of the core and adjacent to the rivet end portions having a boss extending outwardly by a distance substantially equal to the thickness of the opposite end portions, whereby the bosses limit and prevent excessive swelling of the resinous material due to a current overload.

The advantage of the improved electric control apparatus of this invention is the ready removal and replacement of a coil when burn out failure of coil windings OCCUI'.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of an electric control device constructed in accordance with the principles of this invention;

FIG. 2 is an exploded isometric view of the control device shown in FIG. 1;

FIG. 3 is a vertical sectional view taken through one of the poles of the device;

2 FIG. 4 is a vertical sectional view taken along the line IV-IV of FIG. 3;

FIG. 5 is a vertical sectional view through one of the outside laminations of the core; and I FIG. 6 is a plan view taken on the line VI--VI of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings an electric control device or contactor is generally indicated at It). Inasmuch as the contactor is more specifically described in US. Pat. No. 3,368,171, issued Feb. 6, 1968, the description herein is limited generally to the operating parts that are pertinent to the invention.

Generally, the contactor It) comprises a base plate I2, a housing 14 composed of electrically insulated material, and an operating structure generally indicated at 116 in FIG. 3. The contactor I0 is a multi-pole control device of which only one set of poles is shown in FIG. 3 and includes similar movable contacts 18 and stationary contacts 20. The contactor 10, being operated by an electromagnetic actuator includes a molded insulating contact carrier 22 and a generally U-shaped magnetic armature 24.

The electromagnetic actuator also includes a generally U-shaped magnetic core 26 (FIG. 4) and a coil structure 28. The U-shaped core 26 is a laminated member and includes similar side plates 30 on opposite sides thereof. The assembly of the laminated core including the side plates 30 is secured together by rivets 32, the opposite ends of which extend beyond the side plates 30 as shown in FIG. 6. In addition, in accordance with this invention, each side plate 30 comprises a raised portion, protrusion, or boss 34 which extends outwardly from the laminations by a distance substantially equal to the thickness of the end portions of the rivets 32. More particularly, two bosses 34 are provided on each side plate 30, one below each rivet end portion 32. The purpose of the bosses 34 is set forth hereinbelow.

The coil structure 28 comprises a pair of coil windings 36 and 38 which are wound on separate spools or bobbins 4t) and 42, respectively. The assemblies of the windings 36, 38 and bobbins 40, 42 are encapsulated in a molded portion 44 of the housing 14 which portion is detachably mounted (FIG. 2) so that coils of varying ratings may be substituted where conditions require. Moreover, by providing the molded portion 44 as a replaceable unit, its failure for any reason, such as burning out, facilitates replacement and return to service of the contactor 10 with only a brief interruption. More particularly, the molded portion 44 of the housing is composed of an electrically insulating material, such as a phenolic or thermosetting resin, and is provided with a pair of similar openings 46 which receive the upright portions of the U-shaped core 26 when assembled as shown in FIG. 4.

In one embodiment of this invention, where the bobbins 40 and 42 are composed of a thermoplastic resinous material such as nylon, the walls forming the open ings 46 are lined with an internal wrapper or coating 48 (FIG. 6), such as tape of woven glass fiber, having an adhesive coating for ready attachment to the walls of the opening, said coating being disposed in the clearance space 50 between said walls and the upright portions of the core 26. Thus, when an overload current of sufficient magnitude occurs to cause the windings to overheat and melt the bobbins 40 and 42, the melted portions are prevented from flowing or oozing into the area of and adhering to any projections such as the end portions of the rivets 32 and adjacent crevasses on the core 26. Moreover, any swelling or bulging of the molded portion 44 in the area of the bobbins 40 and 42 is restrained or limited by the bosses 34. In other words, the coatings 48 cooperate with the bosses 34 to restrain the melted bobbins 40 and 42 from unlimited flowing core 26 and including the ends of the rivets 32. However, when subjected to a sufficiently high temperature such as developed in the coil windings 36 and 38 during an excessive overload current, the thermosetting material swells or bulges inwardly but is limited in its movement by the bosses 34, thereby enabling subsequent ready removal of the molded portion 44 and its replacement.

As shown in FIG. 4 the molded portion 44 preferably encapsulates the upper and lower and exterior sides of the assembly of the windings and bobbins 40, 42. The

inner surfaces of the bobbins forming the openings 46 may also be covered with the material comprising the molded portion 44. However, the prefabricated bobbin has been found sufficient for providing the surface wall of the openings 46.

In conclusion, the advantage of the circuit interrupter structure of this invention includes primarily the solution of a problem where an armature does not close satisfactorily upon a magnet core due to some reason such as jamming which results in the creation of an air gap which reduces the inductive reactance which, in turn, allows the coil current to increase up to possibly ten times the normal operating current. The resulting increase in current is sufficient to cause overheating of the encapsulating material around the windings including the spools or bobbins on which the windings are mounted so that the insulation and encapsulant becomes physically distended or distorted and causing bulging by expansion and outgassing. The primary object of this invention is to limit the expansion of the insulation to a minimum in order to facilitate removal of the burned out coil from the magnet and its replacement in an expeditious manner.

What is claimed is:

1. An electric control apparatus comprising an insulating housing, pairs of separable contacts within the housing, means within the housing for moving the contacts between open and closed positions and comprising an electromagnetic control mechanism including a magnetic armature, a magnetic core and a coil, the insulating housing including a detachable portion containing the coil, the detachable portion of the housing being composed of a resinous material, the detachable housing portion having walls forming the opening means for receiving the core, the core comprising a plurality of laminations and a rivet securing the laminations together, the rivet comprising opposite end portions extending into clearance space between the core and the walls forming the opening means, each lamination on the opposite sides of the core and adjacent the rivet end portions having a boss extending outwardly by a distance substantially equal to the thickness of the opposite end portions, whereby the bosses limit and prevent excessive swelling of the resinous material due to a current overload.

2. The electric control apparatus of claim 1, in which the detachable portion of the housing is composed of a thermoplastic material, and liner means are mounted on the walls of the opening means for restraining swelling of the walls.

3. The electric control apparatus of claim 2, in which the liner means comprises a glass fiber tape.

4. The electric control apparatus of claim 3, in which the glass fiber tape includes an adhesive coating.

5. The electric control apparatus of claim 1, in which the detachable portion of the housing is composed of a thermosetting resinous material. 

1. An electric control apparatus comprising an insulating housing, pairs of separable contacts within the housing, means within the housing for moving the contacts between open and closed positions and comprising an electromagnetic control mechanism including a magnetic armature, a magnetic core and a coil, the insulating housing including a detachable portion containing the coil, the detachable portion of the housing being composed of a resinous material, the detachable housing portion having walls forming the opening means for receiving the core, the core comprising a plurality of laminations and a rivet securing the laminations together, the rivet comprising opposite end portions extending into clearance space between the core and the walls forming the opening means, each lamination on the opposite sides of the core and adjacent the rivet end portions having a boss extending outwardly by a distance substantially equal to the thickness of the opposite end portions, whereby the bosses limit and prevent excessive swelling of the resinous material due to a current overload.
 2. The electric control apparatus of claim 1, in which the detachable portion of the housing is composed of a thermoplastic material, and liner means are mounted on the walls of the opening means for restraining swelling of the walls.
 3. The electric control apparatus of claim 2, in which the liner means comprises a glass fiber tape.
 4. The electric control apparatus of claim 3, in which the glass fiber tape includes an adhesive coating.
 5. The electric control apparatus of claim 1, in which the detachable portion of the housing is composed of a thermosetting resinous material. 